1. Field of the Invention
The present invention relates to the use of modified carbon products in a number of applications. More particularly, the present invention relates to the use of modified carbon products and metal-functionalized modified carbon products in applications such as catalysis, electronic and ionic conduction, adsorption, heat transfer and luminescence.
2. Description of Related Art
Carbon is used in a wide variety of industrial applications that take advantage of its intrinsic characteristics. These characteristics include good electrical conductivity, high surface area, black color, abrasion resistance and intercalation. The electrical conductivity can be controlled, with graphitic materials being more conductive compared to amorphous carbon. This leads to numerous applications in the battery industry and fuel cell industry where carbon is used as an electrode material. The typically high surface area with somewhat controllable porosity results in the use of carbon in applications such as catalyst and electrocatalyst supports, where the high surface area produces highly dispersed supported catalysts and absorbents. In the case of electrocatalysts, the characteristics of high surface area and electrical conductivity are combined to create conductive catalyzed gas diffusion electrodes.
Carbon is also intensely black and a relatively small amount of carbon can be used to impart an intensely black color to objects. As a result, it is used to fill polymers to make black plastics as well as being used in printing inks to create text and images such as newspaper print or small office/home office printed products. As an extension of this attribute, the inclusion of a filler results in strengthening of the polymer or plastic leading to improved mechanical strength and abrasion resistance and has resulted in the extensive use of carbon in vehicle tires, for example.
In addition, the layer structure of the graphite polymorph of carbon can be intercalated with various materials. An example is lithium in lithium ion batteries.
The surface of the carbon material does not play an active role in most of the foregoing applications. Where it does play a role (e.g., electrocatalysis in zinc-air batteries), it is a very specific role limited to the particular composition of the carbon surface. Indeed, in many applications of carbon materials, the surface of the carbon is coated with surfactants to enhance the dispersion characteristics of the carbon in another medium such as an aqueous, non-aqueous or polymeric vehicle. However, in many applications, the surface chemistry dominates the function of the material in an application, in many cases independent of the characteristics of the bulk material. For example, applications that require reversible specific binding of ions or molecules to surfaces for applications such as sensors, adsorbents, catalysis, power sources, displays, electrodialysis, ionic transport and separations are often independent of the composition of the bulk material. Therefore it would be extremely valuable to have a versatile method to create a wide variety of functionalization on a surface. It would be even more valuable if the surface on which the functionalization is developed is part of a bulk material that has characteristics that further enhance the functionalization of the surface.
A method for the functionalization of carbon products has been described in U.S. Pat. No. 5,900,029 by Belmont et al., which is incorporated herein by reference in its entirety. The process described therein is referred to herein as the Belmont process. It was shown by Belmont et al. that a wide variety of organic functional groups can be chemically bonded to the surface of almost any form of carbon using diazonium salt chemistry. To date, applications of these “surface modified carbons” or “modified carbon products” have focused on improving the dispersion characteristics of the carbon products in other media such as inks, pastes and polymers.
Belmont et al. discloses a modified carbon black product and a method for making a modified carbon black product. The modified carbon black is formed by reacting at least one diazonium salt with carbon black in the absence of an externally applied electric current sufficient to reduce the diazonium salt. It is disclosed that the modified carbon black products can be utilized in plastic compositions, rubber compositions, paper compositions and textile compositions.